1. Field of the Invention
As disclosed in my prior pending applications, Ser. No. 11/529,617, filed Sep. 28, 2006, and Ser. No. 11/363,014, filed Feb. 27, 2006, the present invention relates generally to gas delivery, evacuation and respiratory monitoring systems and methods and more particularly pertains to allowing a user to deliver at least one gas and scavenge the exhausted gas as well as monitor the exhausted gas in a safe and efficient manner. A preferred use for such system and method is the application of anesthesia gas(es) to a patient undergoing surgery. Even more particularly, the present invention relates to new and improved disposable anesthesia face masks which may be used in such systems and methods.
2. Description of the Prior Art
The use of face masks to apply inhalation agents (gases) is well known in the medical treatment art. For example, during the administration of general anesthesia (GA) it is common to ventilate a patient with oxygen during the pre-intubation stage (induction) using a mask coupled to a suitable supply. Sometimes it is necessary to continue to use mask ventilation during surgery when a patient cannot be intubated with an endo-tracheal tube, or during procedures of relatively brief duration. On other occasions, it may be desirable to provide supplemental anesthesia using various anesthesia inhalation agents in the form of a gas selected, for example, from the group consisting of desflurane, sevoflurane, isoflurane, or nitrous oxide, or combinations thereof. Oxygen or the inhalation gas(es) selected by the anesthesia provider typically are applied to a patient using an inhalation face mask connected to a tube or tubes (such tubes commonly being referred to as a breathing circuit) which in turn is connected to a suitable gas supply. Generally, once a patient is ventilated and then intubated with an endo-tracheal tube or the like, the mask is set aside until the end of the procedure when the endo-tracheal tube is removed and the patient briefly is ventilated with O2 through the mask. Exemplary of gas inhalation masks used in administering GA to a patient is that disclosed in U.S. Pat. No. 5,975,079 (Hellings et al). As indicated by this patent, an acceptable anesthesia mask should be disposable, made of transparent material, have a strap or straps to hold the mask in place when desired, be of sufficient size to cover the patient's nose and mouth, and have a pneumatic sealing cushion, not only to promote patient comfort, but to prevent exposing anesthesia or other personnel to the applied gas or gases. This patent (U.S. Pat. No. 5,975,079) hereby is incorporated herein and made part hereof by this reference.
In my prior pending U.S. patent application Ser. No. 11/529,617, filed Sep. 28, 2006, and Ser. No. 11/363,014, filed Feb. 27, 2006, I disclose and claim a face mask which is capable of functioning as an improved anesthesia mask compared to the prior art masks (exemplified by the '079 patent) because my mask in accordance with my inventive concept(s) uniquely combines the following advantages, inter alia: (1) the ability to deliver and evacuate gas(es) while being sealed on the patient's face, (2) the provision of an end-tidal CO2 monitoring port directly on the mask itself in a location promoting extremely accurate CO2 signal tracing and readout, and further, (3) the provision of a mask face having a bottom or basal portion adapted to engage the underside of the chin or jaw of the wearer or patient in such a way as to stabilize the mask on the patient's face without affecting its sealing capability.
During the application of general anesthesia (GA), it has become standard practice to always monitor the patient to assure proper breathing. One way to accomplish this is to detect CO2 present in exhaled air or end-tidal breathing of the patient. This may be done efficiently by providing an end-tidal CO2 port on the breathing circuit attached to the mask or to the endo-tracheal tube and connecting a flexible tube between the port and a device (capnograph) for monitoring end-tidal CO2.
In surgical cases where monitored anesthesia care (MAC) is employed, the patient merely is sedated rather than being paralyzed and intubated (as in GA). It is known to monitor end-tidal CO2 in such cases (MAC) sporadically by employing nasal cannula connected to a capnograph, or by using an oxygen mask with a CO2 sampling tube. For example, a divided-cannula with an O2 line and a CO2 line is commercially distributed by Salter Labs, Arvin, Calif. whereas an oxygen mask with a CO2 sampling tube is commercially distributed by Southmedic under the Capnoxygen® trademark. The failure to efficiently monitor end-tidal CO2 during MAC anesthesia can have adverse medical reactions. Bhananker et al have reported in “Injury and Liability Associated with Monitored Anesthesia Care,” Anesthesiology 2006, 104:228-34, incorporated herein by this reference, that nearly half the claims studied “were judged as preventable by better monitoring including capnography and that patient safety during MAC may be improved by the use of capnography.”
Prior masks used in general anesthesia are designed to cover only the nose and mouth, and therefore (unlike the present invention), the capability of using the patient's chin to anchor and stabilize the anesthesia mask has gone unrecognized. In fact, as disclosed in the '079 patent, when an anesthesia mask of limited extent (i.e. sized and configured to cover only the nose and mouth) is applied to a patient's face, the mask is unstable and must be held in position by hand. Only when a relatively complicated and unwieldy strap or headband assembly is employed to affix the mask in place are anesthesia personnel free to use both hands (see column 2, lines 3-5, in the '079 patent). Even so, because the mask is covering only the nose and mouth of the patient's face such headbands must be applied with a relatively high tension or tightening force to maintain an effective seal. Accordingly, such masks are poorly tolerated by sedated patients and when tightened on a patient's face or head in order to be stabilized, the danger of injury to facial or ocular tissue is presented. Hence, to applicant's knowledge, these masks have not been employed during MAC procedures. By anchoring a sealable mask at the chin (as is disclosed only in my prior application Ser. Nos. 11/363,014 and 11/529,617), the mask is rendered stable and displacement toward the ocular area or elsewhere is prevented under virtually all conditions likely to be encountered during the ensuing surgical procedure. Moreover, a relatively simple headband (elastic) that engages only the periphery of the mask may be employed without excessive pressure and anesthesia personnel do not have to be concerned about also holding the mask in place on the patient's face thereby freeing both hands to attend to other important tasks.
Although the mask disclosed and claimed in my prior application Ser. Nos. 11/363,014 and 11/529,617, overcomes many of the disadvantages of prior art masks particularly with respect to providing chin engagement stability and end-tidal CO2 monitoring capability in a sealable face mask capable of delivering and evacuating gases(s), this form of anesthesia mask is susceptible of still further improvements and refinements not shown nor suggested in the prior art.
Therefore, it can be appreciated that there exists a continuing need for a new and improved disposable anesthesia face mask for use in providing inhalation gas(es) to a patient in the context of a gas delivery, evacuation and respiratory monitoring system and in this regard, the present invention substantially fulfills this need.